UWB (Ultra Wide Band) is focused upon as a radio scheme of ultra low power consumption that enables higher speed compared to conventional mobile telephones and wireless LAN (Local Area Network) and that enables implementation in portable equipment such as mobile telephones. While wireless systems used today perform communication using frequency bands of several dozens of MHz, the UWB wireless system refers to a wireless system that performs communication using bands of several hundreds of MHz to several GHz. Following legislation the main point of which is to allow, as UWB communication, short pulse communication using frequency bands of 3.1 to 10.6 GHz if the frequency band is equal to or less than the unnecessary radiation level of, for example, a personal computer designated in Part 15 according to FCC in the U.S.A. in 2002, UWB communication is actively studied.
As the method for implementing the UWB wireless system, single carrier communication including short pulse communication is regarded promising as a scheme that enables low power consumption. Mainly, there are the amplitude modulation scheme (ASK: Amplitude Shift Keying) and phase modulation scheme (PSK: Phase Shift Keying) as modulation schemes used in single carrier communication. Data is superimposed by the strength of signals according to the amplitude modulation scheme, so that the performance required with respect to the oscillator is low and implementation of the amplitude modulation scheme is anticipated at low cost and at low power consumption. On the other hand, the phase modulation scheme requires an oscillator with low phase noise for superimposing data on the phases of signals, and so requires great power consumption compared to the amplitude modulation scheme. However, the phase modulation scheme does not cause performance deterioration due to threshold value control for deciding between “0's” and “1's,” which is required to demodulate amplitude modulation signals, and provides an advantage for a higher function of realizing higher speed transmission using M-ary phase modulation schemes.
Consequently, UWB communication assumes an environment of usage where there are UWB transmitting apparatuses that perform amplitude modulation and UWB transmitting apparatuses that perform phase modulation using the same frequency band, and realization of a UWB transmitting apparatus using both adequately is demanded.
Patent Document 1 discloses a transmitting apparatus that can support both the amplitude modulation scheme and phase modulation scheme. FIG. 1 shows components of the transmitting apparatus disclosed in Patent Document 1. In this transmitting apparatus, upon ASK modulation, QPSK baseband processing section 1, ASK baseband processing section 2 and common transmission signal processing section 11 generate, according to input data, a zero-value Q-value component and a binary I-value component varying between the intersecting point (i.e. original point) between the I-axis and the Q-axis and a signal point on the I-axis, and input the result to a QPSK modulator. On the other hand, upon. QPSK modulation, ASK baseband processing section 2 and common transmission signal processing section 11 generate a multivalue I-value component and a multivalue Q-value component according to input data and input the result to QPSK modulator 60, in order to perform QPSK modulation and ASK modulation of carriers.
Patent Document 1: Japanese Patent Application Laid-Open No. 2004-147052